onsdag 2. mai 2018

Building on its experience producing electrically powered
motor gliders, Germany’s Lange Aviation set out to develop a surveillance
platform combining long endurance and low emissions with the high
reliability required to carry expensive payloads and the flexibility of
being optionally piloted.

The result is the Antares E2, a fuel-cell-powered aircraft
with 40-hr. endurance when flown unmanned. The prototype was unveiled at
the Aero 2018 general aviation show in Friedrichshafen, Germany, on
April 18, and is expected to make its first flight in June.

The E2 is a follow-on to the Antares DLR-H2,
developed with German aerospace center DLR. Based on an Antares 20E motor
glider, the H2 first flew in 2009 and was the first piloted aircraft to
be powered exclusively by fuel cells. The H2 used pressurized hydrogen as
the fuel.

The Antares E2
uses methanol as the fuel. This is converted to hydrogen for use in the
fuel cells by catalytic steam reformers. The aircraft is designed with
high redundancy and reliability, as the payloads carried by surveillance
platforms can cost 2-3 times as much as the airframe itself.

The E2 has six
reformed methanol fuel cells powering six electric motors via six DC/DC
converters, as well as a quadruplex-redundant flight control system. The
aircraft can maintain horizontal flight on just two of the six motors and
three of the six fuel cells, Lange says.

Propellers are mounted above the wing in
clear air to improve aerodynamics and reduce noise. Credit: Lange Aviation

Fuel cells
minimize fuel consumption and emissions, but the aircraft must run for an
hour before launch to heat the cells to their 170C (330F)
operating temperature. Fuel cells are also slow to respond, so a
lithium-ion battery provides additional power for takeoff, climb and
dynamic flight.

The 6.7-kW fuel
cells are housed in two large pods under the inboard section of the
23-m-span (75.6-ft.) wing, and 300 kg (660 lb.) of methanol fuel is
stored in outboard wing pods. The battery—24 modules each with three
cells—is installed in the leading edge of the wing.

Methanol fuel is steam reformed into
hydrogen for use in the fuel cell, pictured next to the aircraft. Credit:
Aero 2018

The 15-kW motors
and propellers are mounted on struts high above the trailing
edge of the wing. This arrangement results in no aerodynamic interference
from the props on the airflow over the upper and lower surfaces of the
wing, says Lange.

Payloads can be
installed in forward- and mid-fuselage bays and the outboard wing pods.
The Antares E2 can carry 200 kg of payload and provide 4 kW of power for
sensors and other systems. This is more than enough for the civilian
applications at which the E2 is aimed, says Lange.

The E2 will fly
initially with a pilot, but Lange plans to develop it as an unmanned
aircraft for long-endurance missions including maritime surveillance,
security, border control and surveying. The company plans to certify the
aircraft to European CS-23 regulations, although the airworthiness rules
for unmanned operation are not yet in place.